package cn.newtouch.nio;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.net.ServerSocket;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.util.Iterator;
import java.util.Set;

public class NIOServer
{

    /* 标识数字 */
    private int        flag          = 0;

    /* 缓冲区大小 */
    private int        BLOCK         = 4096;

    /* 接受数据缓冲区 */
    private ByteBuffer sendbuffer    = ByteBuffer.allocate(this.BLOCK);

    /* 发送数据缓冲区 */
    private ByteBuffer receivebuffer = ByteBuffer.allocate(this.BLOCK);

    private Selector   selector;

    public NIOServer(int port) throws IOException
    {
        // 打开服务器套接字通道
        ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
        // 服务器配置为非阻塞
        serverSocketChannel.configureBlocking(false);
        // 检索与此通道关联的服务器套接字
        ServerSocket serverSocket = serverSocketChannel.socket();
        // 进行服务的绑定
        serverSocket.bind(new InetSocketAddress(port));
        // 通过open()方法找到Selector
        this.selector = Selector.open();
        // 注册到selector，等待连接
        serverSocketChannel.register(this.selector, SelectionKey.OP_ACCEPT);
        System.out.println("Server Start----" + port);
    }

    // 监听
    public void listen() throws IOException
    {
        while (true)
        {
            // 选择一组键，并且相应的通道已经打开
            this.selector.select();
            // 返回此选择器的已选择键集。
            Set<SelectionKey> selectionKeys = this.selector.selectedKeys();
            Iterator<SelectionKey> iterator = selectionKeys.iterator();
            while (iterator.hasNext())
            {
                SelectionKey selectionKey = iterator.next();
                iterator.remove();
                this.handleKey(selectionKey);
            }
        }
    }

    // 处理请求
    private void handleKey(SelectionKey selectionKey) throws IOException
    {
        // 接受请求
        ServerSocketChannel server = null;
        SocketChannel client = null;
        String receiveText;
        String sendText;
        int count = 0;
        // 测试此键的通道是否已准备好接受新的套接字连接。
        if (selectionKey.isAcceptable())
        {
            // 返回为之创建此键的通道。
            server = (ServerSocketChannel) selectionKey.channel();
            // 接受到此通道套接字的连接。
            // 此方法返回的套接字通道（如果有）将处于阻塞模式。
            client = server.accept();
            // 配置为非阻塞
            client.configureBlocking(false);
            // 注册到selector，等待连接
            client.register(this.selector, SelectionKey.OP_READ);
        }
        else
            if (selectionKey.isReadable())
            {
                // 返回为之创建此键的通道。
                client = (SocketChannel) selectionKey.channel();
                // 将缓冲区清空以备下次读取
                this.receivebuffer.clear();
                // 读取服务器发送来的数据到缓冲区中
                count = client.read(this.receivebuffer);
                if (count > 0)
                {
                    receiveText = new String(this.receivebuffer.array(), 0, count);
                    System.out.println("服务器端接受客户端数据--:" + receiveText);
                    client.register(this.selector, SelectionKey.OP_WRITE);
                }
            }
            else
                if (selectionKey.isWritable())
                {
                    // 将缓冲区清空以备下次写入
                    this.sendbuffer.clear();
                    // 返回为之创建此键的通道。
                    client = (SocketChannel) selectionKey.channel();
                    sendText = "message from server--" + this.flag++;
                    // 向缓冲区中输入数据
                    this.sendbuffer.put(sendText.getBytes());
                    // 将缓冲区各标志复位,因为向里面put了数据标志被改变要想从中读取数据发向服务器,就要复位
                    this.sendbuffer.flip();
                    // 输出到通道
                    client.write(this.sendbuffer);
                    System.out.println("服务器端向客户端发送数据--：" + sendText);
                    client.register(this.selector, SelectionKey.OP_READ);
                }
    }

    public static void main(String[] args) throws IOException
    {
        NIOServer server = new NIOServer(8888);
        server.listen();
    }
}
